Acoustic Path Microphone Placement for Feed-Forward Noise Cancellation
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Solution Overview
Problem
Existing noise cancelling systems in sound output devices face challenges with system stability and noise attenuation, particularly in the mid-to-high frequency range due to individual differences in ear shape and wearing state, and the difficulty in achieving sufficient noise reduction using feed-forward techniques.
Innovation Solution
A sound output device with an acoustic path connecting a front surface and outside of a driver unit separately from a back surface, and a microphone disposed near the connection point of this acoustic path to the outside, enhancing noise cancellation by improving the feed-forward technique's noise attenuation capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a noise cancelling system uses feed-forward technique with conventional microphone placement, then noise attenuation is attempted, but system stability deteriorates and noise reduction effectiveness is insufficient especially in mid-to-high frequency range
Solution Approach 1:
The acoustic path is segmented into separate inlet and outlet portions, with the microphone positioned at the inlet. This segmentation allows independent optimization of noise collection (at the inlet) and sound output (at the outlet), improving both stability and noise attenuation effectiveness.
Solution Approach 2:
The acoustic path acts as an intermediary structure that connects the external environment to the driver unit while maintaining spatial separation between noise collection and sound output paths. This intermediary design enables effective noise cancellation without compromising system stability.
2Device complexity
If microphone is placed far from the driver unit, then device structure is simpler, but noise collection effectiveness deteriorates
Solution Approach 1:
The microphone is positioned at a specific local position (inlet of acoustic path) where noise collection effectiveness is maximized. This localized placement ensures precise noise measurement without requiring complex overall device restructuring.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution further reduces external noise and improves system stability, achieving a significant noise reduction effect, especially in the mid-to-high frequency range, by strategically placing the microphone to collect noise closer to its source and using an acoustic path that attenuates noise effectively.
Implementation Method 1
an acoustic path connecting a first space on a front surface of a driver unit and an outside of a housing including the driver unit separately from a second space on a back surface of the driver unit
Implementation Method 2
a microphone disposed in the vicinity of an opening where the acoustic path is connected to the outside of the housing
Data Source
AI summary
A sound output device according to an embodiment includes: an acoustic path (70) and a microphone (100b). The acoustic path connects a first space (54b) formed on a front surface of a driver unit (106) and the outside of a housing (50b) including the driver unit separately from a second space (55b) formed on a back surface of the driver unit. The microphone is disposed in the vicinity of an opening where the acoustic path is connected to the outside of the housing.